This invention relates to (a) novel processes for evaporating liquid from a chemical sample with drying gas, for like processes, and (b) and apparatus useful in such processes.
It is often desirable to transfer a solute from one solvent system to another solvent system. For example, this procedure is used frequently in liquid chromatography where a solution, perhaps a liquid fraction obtained from one chromatographic procedure, can be more specifically analyzed by use of a different solvent. In the past, it has been common to place the first solution into a tube and, using a gas sparge tube, or cannula, contact the solution with sufficient drying gas to remove the unwanted liquid.
A number of problems are associated with this procedure: The incoming gas flow tends to interfere with the outgoing gas flow and the efficiency of the process, including the uniformity of drying is reduced. This leads to imperfectly dried samples, excessive preparatory time, or both. In turn, these problems increase the probability of operator error and samples which are poorly prepared for further processing. Also, where substantial numbers of such operations are carried out, there is a tendency to pollute the air of a laboratory. All these problems are accentuated when one attempts to use relatively warmer, and hence more efficient, evaporating gas.